11,765 research outputs found
Translational Symmetry Breaking in Higgs & Gauge Theory, and the Cosmological Constant
We argue, at a very basic effective field theory level, that higher dimension
operators in scalar theories that break symmetries at scales close to their
ultraviolet completion cutoff, include terms that favour the breaking of
translation (Lorentz) invariance, potentially resulting in striped, chequered
board or general crystal-like phases. Such descriptions can be thought of as
the effective low energy description of QCD-like gauge theories near their
strong coupling scale where terms involving higher dimension operators are
generated. Our low energy theory consists of scalar fields describing operators
such as and . Such scalars can have kinetic
mixing terms that generate effective momentum dependent contributions to the
mass matrix. We show that these can destabilize the translationally invariant
vacuum. It is possible that in some real gauge theory such operators could
become sufficiently dominant to realize such phases and it would be interesting
to look for them in lattice simulations. We present a holographic model of the
same phenomena which includes RG running. A key phenomenological motive to look
at such states is recent work that shows that the non-linear response in
gravity to such short range fluctuations can mimic a cosmological constant.
Intriguingly in a cosmology with such a Starobinsky inflation term, to generate
the observed value of the present day acceleration would require stripes at the
electroweak scale. Unfortunately, low energy phenomenological constraints on
Lorentz violation in the electron-photon system appear to strongly rule out any
such possibility outside of a disconnected dark sector.Comment: 9 pages, 1 figure; minor changes. Version to be published in PR
A class of symplectic integrators with adaptive timestep for separable Hamiltonian systems
Symplectic integration algorithms are well-suited for long-term integrations
of Hamiltonian systems because they preserve the geometric structure of the
Hamiltonian flow. However, this desirable property is generally lost when
adaptive timestep control is added to a symplectic integrator. We describe an
adaptive-timestep symplectic integrator that can be used if the Hamiltonian is
the sum of kinetic and potential energy components and the required timestep
depends only on the potential energy (e.g. test-particle integrations in fixed
potentials). In particular, we describe an explicit, reversible, symplectic,
leapfrog integrator for a test particle in a near-Keplerian potential; this
integrator has timestep proportional to distance from the attracting mass and
has the remarkable property of integrating orbits in an inverse-square force
field with only "along-track" errors; i.e. the phase-space shape of a Keplerian
orbit is reproduced exactly, but the orbital period is in error by O(1/N^2),
where N is the number of steps per period.Comment: 24 pages, 3 figures, submitted to Astronomical Journal; minor errors
in equations and one figure correcte
Development of a Computerized Infectious Disease Monitor (CIDM)
journal articleBiomedical Informatic
Chevalier Jackson, M.D. (1865-1958): Il ne se repose jamais.
In the final year of the American Civil War, 1865, Chevalier Jackson was born on the 4th of November just outside Pittsburgh, Pennsylvania. The eldest of three sons of a poor, livestock-raising family, Jackson was raised in a period of social and political unrest. He was perhaps an even more unrestful boy. The description of his childhood days from his father’s father—Il ne se repose jamais, ‘‘He never rests’’—would ultimately reflect the man, doctor, and evangelist Jackson would later become.1 Indeed, he never did rest, Jackson would tirelessly pave the way for modern bronchoscopy and endoscopy as a whole; bringing international renown not only to himself, but also to his specialty
The Effects of the Transcription Factor IRF-3 in Pam2ODN Microbial Resistance
https://openworks.mdanderson.org/sumexp23/1092/thumbnail.jp
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Reaction Bonded Silicon Carbide: SFF, Process Refinement and Applications
Reaction bonded silicon carbide (RBSiC) has a wide variety of industrial applications and
a manufacturing process based on Selective Laser Sintering (SLS) has been demonstrated in
previous research at the University of Texas. That study was directed toward semiconductor
manufacturing applications and was based on prior indirect SLS methods. Several key research
questions were addressed for three main manufacturing phases: preform SLS, binder burnout and
reactive infiltration. The current research is focused on development of material systems and
manufacturing capability and is directed toward a broader set of potential applications. Preform
formation utilizes SiC powder of an appropriate average particle size mixed with a multicomponent binder. The preform or green part is then placed in a vacuum furnace to carbonize
the binder. The details of the binder chemistry must support accurate SFF shapes and acceptable
surface roughness, a strong green part and maintenance of the part shape during the first furnace
operation. Finally, the physics and chemistry of the infiltration process, based on the
microstructure of the initial green preform, determine the viability of the manufacturing process
and the characteristics of the final composite material.
The functionality of metal, polymer and ceramic matrix composites can support the
growing SFF industry desire to move beyond functional prototyping and into manufacturing
arenas. This project is being explored for more general application to matrix composite
materials, especially highly functional systems tailored specifically for SLS. The goal is to
establish the governing principles of binder function, carbonization and infiltration as well as to
understand the interdependence of these phases in terms of manufacturing application. With this
understanding new applications and special SLS composites can support the development of new
products and a greater SFF manufacturing presence.
This paper provides an introduction to the material, a look at basic rapid manufacturing
trends, an overview of the previous work, a review of relevant RBSiC material science issues,
and an outline of the current study.Mechanical Engineerin
Effect of varying the concentrations of carbohydrate and milk protein in rehydration solutions ingested after exercise in the heat
The present study investigated the relationship between the milk protein content of a rehydration solution and fluid balance after exercise-induced dehydration. On three occasions, eight healthy males were dehydrated to an identical degree of body mass loss (BML, approximately 1.8 %) by intermittent cycling in the heat, rehydrating with 150 % of their BML over 1 h with either a 60 g/l carbohydrate solution (C), a 40 g/l carbohydrate, 20 g/l milk protein solution (CP20) or a 20 g/l carbohydrate, 40 g/l milk protein solution (CP40). Urine samples were collected pre-exercise, post-exercise, post-rehydration and for a further 4 h. Subjects produced less urine after ingesting the CP20 or CP40 drink compared with the C drink (P<0.01), and at the end of the study, more of the CP20 (59 (SD 12) %) and CP40 (64 (SD 6) %) drinks had been retained compared with the C drink (46 (SD 9) %) (P,0.01). At the end of the study, whole-body net fluid balance was more negative for trial C (2470 (SD 154) ml) compared with both trials CP20 (2181 (SD 280) ml) and CP40 (2107 (SD 126) ml) (P<0.01). At 2 and 3 h after drink ingestion, urine osmolality was greater for trials CP20 and CP40 compared with trial C (P<0.05). The present study further demonstrates that after exercise-induced dehydration, a carbohydrate–milk protein solution is better retained than a carbohydrate solution. The results also suggest that high concentrations of milk protein are not more beneficial in terms of fluid retention than low concentrations of milk protein following exercise-induced dehydration
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Prevalence of axial spondyloarthritis in patients with inflammatory bowel disease using cross-sectional imaging: a systematic literature review.
BACKGROUND: Patients with inflammatory bowel disease (IBD) have an excess burden of axial spondyloarthritis (axSpA), which, if left untreated, may significantly impact on clinical outcomes. We aimed to estimate the prevalence of axSpA, including previously undiagnosed cases, in IBD patients from studies involving cross-sectional imaging and identify the IBD features potentially associated with axSpA. METHODS: PubMed, Embase and Cochrane databases were searched systematically between 1990 and 2018. Article reference lists and key conference abstract lists from 2012 to 2018 were also reviewed. All abstracts were reviewed by two authors to determine eligibility for inclusion. The study inclusion criteria were (a) adults aged 18 years or above, (b) a clinical diagnosis of IBD and (c) reporting identification of sacroiliitis using cross-sectional imaging. RESULTS: A total of 20 observational studies were identified: 12 used CT, 6 used MR and 2 utilised both computed tomography (CT) and magnetic resonance (MR) imaging. Sample sizes ranged from 25 to 1247 (a total of 4096 patients); 31 studies were considered to have low selection bias, 13 included two or more radiology readers, and 3 included rheumatological assessments. The prevalence of sacroiliitis, the most commonly reported axSpA feature, ranged from 2.2% to 68.0% with a pooled prevalence of 21.0% [95% confidence interval (CI) 17-26%]. Associated IBD features include increasing IBD duration, increasing age, male sex, IBD location, inflammatory back pain and peripheral arthritis. No significant difference in the prevalence of sacroiliitis between Crohn's disease and ulcerative colitis was identified. Study limitations include variability in the individual study sample sizes and patient demographics. CONCLUSION: This review highlights the need for larger, well-designed studies using more sensitive imaging modalities and multivariable modelling to better estimate the prevalence of axSpA in IBD. An improved knowledge of the IBD phenotype(s) associated with axSpA and use of cross-sectional imaging intended for IBD assessment to screen for axSpA may help clinicians identify those patients most at risk
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